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THE CELL THEORY

THE CELL THEORY. 1. What level of complexity is necessary for life?. Aristotle (384 – 322BC). What level of complexity is necessary for life?. C17th microscopists discovered tissues were made of cells (Hooke 1665 and Leeuwenhoek 1677)

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THE CELL THEORY

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  1. THE CELL THEORY 1

  2. What level of complexity is necessary for life? • Aristotle (384 – 322BC)

  3. What level of complexity is necessary for life? • C17th microscopists discovered tissues were made of cells (Hooke 1665 and Leeuwenhoek 1677) • C18th and C19th showed that tissues were made of cells and that the cells of a particular tissue had a common structure

  4. Organism Organ-system Organ Tissue Cell What level of complexity is necessary for life? • Xavier Bichat (1771-1802): An organ is composed of different tissues and several organs can be grouped together as an organ system (e.g. the digestive system) • An idea of hierarchy of structure developed:

  5. What level of complexity is necessary for life? • Purkinje (1835) Observed a fertilised hen's egg (a single cell) could develop into an embryo (many specialised cells in a compact mass) and named tHe cell content -PROTOPLASM • C19th botanists showed that plant tissues consist of many different types of cells

  6. THE CELL THEORY • Matthias Schleiden (1838) & Theodor Schwann (1839) “The cell is the basic unit of living tissue” • The cell is an autonomous unit grouped together to form an organism • Rudolf Virchow (1858) noted that: “all cells come from pre-existing cells”

  7. Cell theory • That the cell is the basic and smallest unit of life • All living organisms are made up of cells. • Cells come from pre-existing cells.

  8. Unicellular Organisms-fully functional individual organisms • Metabolism • Response to stimuli • Growth • Reproduction • Homeostasis-maintaining stable condition inside the body • nutrition

  9. More is different! In multicellular • As a multicellular organism grows and develops it follows a structured plan • The cells specialise (differentiate) • The whole organism shows homeostatic control • A developing multicellular organism shows emergent properties • It is not just a the sum of the parts

  10. THE ORGANISMAL THEORY The counter argument: • Reichert a morphologist: Argued that an organism has a structured plan • Strasberger a cytologist: Cells are connected in an organism sometimes by cytoplasmic bridges (plant cell plasmodesmata) • Sherrington and Pavlov neurophysiologists: Cells communicate with one another and they are co-ordinated in their actions

  11. 2. Certain cells lack the basic components Cells in multicellular organisms are highly specialised Unicellular organisms have a cytoplasm that is not subdivided Should be considered as acellular 2. The basic components of the cell are repeated in every cell 1. Some organisms are not divided into cellular compartments = non-cellular 1. Multicellular organisms develop from a single fertilised germ cell (the zygote) THE CELL THEORY THE ORGANISMAL THEORY SUMMARY

  12. 4. Homeostatic control and co-ordination is required to maintain the whole organism whether it is unicellular or multicellular. 3. Remove cells from complete multicellular organisms requires elaborate life support systems to keep them alive 3. Cells can be taken from organisms and cultured away from the body New individuals can be cultured from isolated cells Regeneration capacity = totipotence THE ORGANISMAL THEORY THE CELL THEORY SUMMARY

  13. Relative sizes • Molecules-1nm • Thickness of membrane-10 nm • Viruses-100nm • Bacteria-1um • Organelles –upto 10 um • Most cells-upto 100um

  14. Emergent properties- arise from the interaction of the component parts; the whole is greater than the sum of the parts.

  15. Multi cellular organisms differentiate to carry out specialized functions by expressing some of there genes but not others.

  16. Euchromatin – light grey—genes that are used (transcribed) • Heterochromatin- dark grey----------- ----------inactive gene

  17. Stem cells • Totipotent—eg, embryo, • Umbilical cord of a new born baby—blood cells—multipotent—limited number of other particular type of cells • Adult ---bone marrow---cells used to treat Leukemia

  18. Zygote-----blastocyst----these cells can become any type of tissue ---pluripotent

  19. Different to normal cells • Undifferentiated • Self sustaining • In presence of chemical signal they can differentiate into specialised cells.

  20. HW • Outline one therapeutic use of stem cells.

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